Modern communications and network equipment often necessitates supplying of electrical power to a multiple number of electrical devices connected to a single electrical hub which provides data connection to the multiple number of electrical devices. In one example, the electrical hub can connect a network equipment (e.g. a network switch, a router, a server, and etc.) with one or more local area network (LAN) data line input and multiple LAN outputs to the multiple number of electrical devices.
A traditional way of supplying power to an electrical device is using a dedicated power supply connection from a DC or AC source to a power input of an electrical device. Sometimes a power adapter plays an intermediary role to convert AC power to DC power before an acceptable input power is supplied to an electrical device. This traditional power supply connection usually requires cumbersome and inconvienient wiring and maintenance, especially if electrical devices are mounted on top of a communication tower (i.e. cellular macro/micro/pico-cell towers, IEEE 802.11-compliant data access points, surveillance cameras, and etc.) or somewhere outdoors.
“Power-over-Ethernet,” commonly known as “PoE” in shorthand, is a useful concept which is gaining recognition in the telecommunications and electronic industries today. Instead of requiring dedicated power supply lines, Power-over-Ethernet delivers a useful electrical power using a conventional RJ45-based Ethernet cable while simultaneously supplying required data as an Ethernet cable to an electrical device.
An industry standard, commonly known as IEEE 802.3af, has formed around the Power-over-Ethernet technology several years ago. The IEEE 802.3af standard allows power sourcing equipments to provide desired power via conventional Ethernet cables to electrical devices. The IEEE 802.3af standard operates based on a device-compliance detection scheme. In one example, an IEEE-802.3af-compliant powered device places a 25 k-ohm resistor between powered pairs of an Ethernet input connector.
If an IEEE 802.3af power sourcing equipment detects a resistance that substantially exceeds or underperforms the required 25 k-ohm resistance at the powered pairs of an electrical device connected by an Ethernet cable, the power source equipment realizes that the electrical device is not IEEE 802.3af-compliant and no power is supplied via the Ethernet cable. On the other hand, if the IEEE 802.3af power sourcing equipment detects a resistance of approximately 25 k-ohm at the powered pairs of an electrical device connected by an Ethernet, then the power source equipment realizes that the electrical device is IEEE 802.3af-compliant and begins to supply power to the electrical device. The IEEE 802.3af standard also supports a “power class” detection scheme, which allows powered devices to indicate their power requirements by changing the sense resistance at higher voltages.
In practice, the IEEE 802.3af standard brings several real-life drawbacks for both power souring equipment and powered devices. Many Ethernet-powered devices and their manufacturers today are reluctant to implement IEEE 802.3af standard due to a relatively high cost of standard integration into their devices, which make their products more expensive than competitors. Furthermore, the IEEE 802.3af-compliance detection scheme makes maintenance and debugging difficult for connected devices to a power sourcing equipment. For instance, if a power sourcing equipment is a PoE network switch with a multiple number of input ports and a multiple number of output PoE ports, it is difficult to troubleshoot an IEEE 802.3af-mode-only powered device which may or may not suffer from a faulty power requirement detection scheme based on the IEEE 802.3af standard. Moreover, for outdoor power applications which needs to supply a relatively high amount of power (e.g. for wireless LAN access points, micro/pico cellular towers, surveillance cameras, and etc.) to Ethernet-powered devices than IEEE 802.3af standard's power supply limitations, relying solely on the IEEE 802.3af is undesirable. Therefore, a new type of power sourcing equipment is desired for Power-over-Ethernet applications which resolves or mitigates the drawbacks of relying entirely on the IEEE 802.3af standard.